In the wild, animals such as badgers are blamed for outbreaks of tuberculosis in cows but this is a difficult issue to prove since it is difficult to establish that contact between the different species has occurred.
In modern livestock farming, animals are moved a large number of times during their lifetimes. For breeding stock, the animals are normally reared on a specialist livestock farm before being transferred to other livestock farms to see out their productive lives. This transfer is usually not direct but is likely to involve an auction market, at least one livestock dealer (but frequently more) and two haulage contractors. Breeding animals at the end of their productive lives are then sent for slaughter. This again is rarely a direct transaction with animals usually passing through a cull stock market before finally reaching an abattoir or renderer.
The pathway for prime meat animals is usually more convoluted than that of breeding stock. Animals may be reared and finished (obtain a weight and fat cover appropriate for slaughter) on their farm of origin. This is the simplest system and involves the least number of animal movement transactions. Typically, either finished animals will be sold directly to the abattoir or they will be sold through a fat stock market, before being transferred to the abattoir. Finally, the abattoirs transfer the meat to wholesalers and retailers. Whereas the majority of pigs are reared and finished on their farm of origin, a relatively high proportion of calves and lambs are sold as store animals. Store animals require a period, of variable length, on high nutrition before they reach a condition ready for slaughter.
The store to finish pathway involves a large number of animal movements with animals being transferred initially from their rearing farms to store markets. Thereafter, they are purchased by dealers who group animals according to breed, weight, size etc before selling on usually to another dealer. These animals are eventually sold to a finisher who will take the animals through to slaughter weight. The pathway from this point is the same as for animals finished on their farm of origin. They are either sold directly to abattoirs or initially to fat stock markets and then to the abattoir.
All these movement transactions generate a mass of associated paperwork, especially, in the United Kingdom, in the case of cattle where a national mainly paper-based passport system operates. This large number of animal movements makes tracking animals very difficult. As consumers increasingly demand assurances concerning animal welfare and validation of preferred production systems, such as organic, the need to track accurately animals as they move down the production chain is increasing. In addition, the moving and mixing of animals at each step in these pathways is of considerable importance in the spread of infectious diseases. The large numbers of infected animals and the rapid spread of foot and mouth disease have vividly demonstrated this.
Various means are known for keeping track of animal movements. The first, and least sophisticated, is a plastic ear tag on which is printed a unique identifier such as a number and/or letter sequence. Such a system requires manual records to be kept, which can result in inaccuracies and omissions. Also known are electronic transponders such as those made by Allflex New Zealand Limited. These devices contain an electronic transponder which can be read by an electronic reader. An example of such a device is described in International Patent Application No. WO93/22907.
A more sophisticated electronic system is described in International Patent Application No. WO99/45761. In this system an electronic device incorporates an electronic radio frequency identification device that can be read by a reader. The electronic device stores information relating to a specific animal such as a unique identifier, inoculation information, feeding information, health etc. The electronic device may be carried on a collar or ear tag, implanted in the animal or provided as a bolus, to be swallowed by the animal and maintained in the stomach.